In vacuum product containerization, it is quite desirable for the protection of the manufacturer, the retailer and the consumer to be able to readily determine if the initial vacuum pressure at the point of container closing has been maintained fully to the point of consumer purchase and use. Recent times have illustrated the problems attendant on food vacuum packed in containers pressurized properly at the manufacturing location and which have lost vacuum to the extent of having been subjected to air to create sufficiently high bacteria in packaged foods to cause illness and loss of life. Apart from this most significant problem, there is the further potential monetary loss attending product recall, immediate loss of respect for the product involved and its manufacturer and general wariness as to further purchase thereof with the passage of time.
While various closure structures for output vacuum pressure indication are shown in patents, all are considered by applicants herein to be unduly complex and difficult to manufacture at appropriate cost.